Refrigerant Compressor Torque Control to Reduce Low-Speed Noise
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Solution Overview
Problem
Variable-speed reciprocating refrigerant compressors experience noise-related issues and vibration excitation at low rotational speeds, leading to undesirable noise emissions during operation and stopping processes, due to varying load torque and lack of counteracting operating torque.
Innovation Solution
An electronic control system that dynamically adjusts the operating torque during each crankshaft revolution by providing a positive operating torque during the compression phase and a reduced or zero torque during the suction phase, allowing for uniform speed and reduced shocks, thereby preventing vibration excitation and noise emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the reciprocating refrigerant compressor is operated at low rotational speeds, then energy consumption is reduced and refrigeration requirements are met, but noise emissions increase due to vibration excitation from varying load torque
Solution Approach 1:
The electronic control device applies operating torque periodically during specific crank angle ranges (drive angle sections) rather than continuously. This periodic torque application compensates for the varying load torque during compression and suction phases, preventing speed fluctuations that excite vibrations at low rotational speeds, thereby reducing noise emissions while maintaining energy efficiency
Solution Approach 2:
The control system dynamically adjusts the operating torque parameter based on the crank angle position and rotational speed. By modifying the torque magnitude and application timing according to operating conditions, the system maintains uniform speed at low rotational speeds without excessive energy consumption, resolving the contradiction between energy savings and noise reduction
2Device complexity
If constant voltage is applied to the drive unit, then control simplicity is maintained, but speed uniformity deteriorates due to uncompensated load torque variations
Solution Approach 1:
The system implements periodic torque application during drive angle sections within each crankshaft revolution. This periodic control approach maintains relatively simple electronic control logic while effectively compensating for load torque variations, achieving uniform speed without requiring complex control algorithms or additional hardware
Solution Approach 2:
The electronic control device uses feedback from rotational speed detection to adjust torque application timing and magnitude. The control system detects actual speed and modifies operating torque in subsequent cycles to maintain uniform speed, achieving stable operation with straightforward feedback control rather than complex predictive algorithms
3Loss of time
If the compressor is stopped by switching off the drive unit, then stopping time is reduced, but noise emissions increase due to uncontrolled load torque effects during coasting
Solution Approach 1:
Before switching off the drive unit, the control device applies operating torque during drive angle sections to maintain uniform rotational speed and prevent excessive speed fluctuations. This preliminary torque application ensures that when the drive is switched off, the compressor is less susceptible to vibration excitation during coasting, reducing noise emissions without extending stopping time
Solution Approach 2:
The control system continues periodic torque application during the final revolutions before shutdown. This maintains speed uniformity during the transition phase, ensuring that the coasting period after switch-off starts from a more stable rotational state, thereby reducing noise from uncontrolled load torque effects while keeping stopping time short
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables quiet operation at low rotational speeds and controlled stopping without the need for braking torque, ensuring the compressor runs smoothly and reduces the risk of piston reversal and noise during the stopping process.
Implementation Method 1
It is possible to determine the relative position of the rotor of the DC motor and thus also the rotational speed of the motor or the compression mechanism on the basis of the counter-voltage (induction counter-voltage) induced in the motor winding
Data Source
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AI summary
The invention relates to an electronic control device (13) for a refrigerant compressor, comprising at least: a drive unit (18); and a compression mechanism (5) which is actively connected to the drive unit (18), with at least one piston (9) which is driven by a crankshaft (6) and moves back and forth between a lower and an upper dead point in a cylinder of a cylinder block (8), in which the electronic control device (13) is designed to detect, control and/or regulate the rotational speed (ω) of the drive unit (18) and to at least approximately detect the piston position, and in which the electronic control device (13) is designed to drive the compression mechanism (5) by means of the drive unit (18) in such a way that at least one drive angle segment (ΔΦ) and at least one transit angle segment (Δτ) is provided for the duration of a regulating time interval (Δt) comprising more than one crankshaft rotation, for a plurality of crankshaft rotations, preferably for each crankshaft rotation of the regulating time interval (Δt), and the compression mechanism (5) is subject to a positive operating torque (Bm) during the at least one drive angle segment (ΔΦ), and to a smaller positive operating torque (Bmv) compared to the positive operating torque (Bm) or to no positive operating torque (Bm) during the at least one transit angle segment (Δτ).